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V8 Motor Options and Questions

CcanDo said:
spinzone/Ben & Suzy, FYI, two each, tuned, w/factory drivers, Manitou's w/300 Evinrudes, running together, tried to compete....They couldn't handle the Benny, LOL.

Call it obnoxious or not, I prefer to be competitive.
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Well the problem there is obvious.....Etecs. The powerheads were already going bad LOL! Same HP on each hull......I stand by my original post. Handling....they are already headed the other direction while you were mid-turn LOL.
 
The Etec powerheads explain why there were two of them....A back up, just in case. For handling, you have a point, the Bennington is SOoo much longer. One has to be careful not to wipe someone out. (Turn Signals..??) Now, the Manitou (being kinda short, not going very fast) might tie the bow to a bouy and skid the transom around. Or, it may be an optical illusion. LOL..... In fact, the Manitou could also be fitted with an engine on each end, that should create a quick directional change. LOL
 
A friend of mine has a 24 Manitou SHP with a 250 Etec. It runs strong, just not for long. He's on powerhead number 3 and looks like BRP may have finally got it right. I ran Mercury 2.5's.... 260, 280, Drag, and Champ motors on my tunnel boats. I ran a full mod, long rod / top guide Yamaha 2.6 until 2002, when I switch to Mercury. I'm no stranger to proper set-up. On our Benningtons...... we like em quiet, smoke / odor free, and reliable. Our choice is Suzuki and Yamaha in that order.
 
I could tell this is not your first Rodeo.....I have always bled black until the EPA messed things up. I still do on Mercury's I/O stuff. The 250 XS has a decent reputation and the 300 XS is hit and miss. I don't know much about the smaller outboards. However, Mercury knows what the gear-box will hold on either O/B or I/O. I've seen several try making a little more power, only to break something.

I don't know anything about the Suzuki and not much more about the Yamaha. Insight comes from offshore racers that are friends with coastal distributors. The report has commercial fishermen going out day after day, adding up several hunded hours on the 350 Yam., with min problems. The gear-box looks like it might be a little stronger, also. The engine starts good, idles good, pulls fairly hard (maybe a little lazy) and fuel consumption is what their fuel flow graph states.

You mentioned ride attitude as being bow high with a heavy engine. IMHO, the hull CG is to far forward. The bow plows unless wt/arm picks up the bow, thus the heavier engine/jack plate just holds the bow high enough. A trim tab inside the center pod, or center tube, creating a controlable step, should have a similar effect.
 
With the newer seating / deck arrangement on the newer boats like yours, which puts the seating / weight farther forward, I would think that the addition of a jackplate would not offset the balance near as much as the older boats like mine. The jackplate did very little for any performance gain for my boat, but with your deck layout, I'm sure it actually did improve the balance and made the boat run with the proper attitude. Being that you own a couple of rather large tunnel boats, you know exactly what I meant by proper "attitude" of the boat. Getting everything adjusted just right can make quite a difference. Performance increases are minimal when dealing with a pontoon vs a hi-perf boat, but any gain is worth the time.

You made an excellent choice with the Yamaha F350. The Yamaha and Suzuki 4 strokes are the real deal for trouble free recreational use. I had a Merc 225XS for a short time. Good running motor. I sold it before the compressor gave out LOL!
 
Adding rigidity to the transom, thereby eliminating ocillation of the tube/transom was a dramatic improvement. The tube/transom not only moved positive and negative, rotational also. The positive/negative movement induced porpoise and scrubbed speed. The rotational movement effected vertical CG, carving, induced tube/transom/hull stress and allowed the hull to wallow in the turn. Stress porpoise was worse in the turn than straight away.

The other point of interest found was a drain hole in the bilge at the bottom of the center tube. Production had used a plasma torch to create said drain hole. We used a 1/2", SS carriage bolt to plug the hole. The result was a couple MPH increase. (They may not punch that hole any longer)

Another project was adding a 4' splash shield. The factory design had the shield ending 4' from the bow. The bottom of the deck was exposed to water and the cross members were exposed to turbulence and water. The effect was seen as tripping the hull and water saturating the wood. The addition created a good solution.
 
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